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RedEaredSlider writes "An asteroid that once was seen as a danger to the Earth may soon provide a once-in-a-century opportunity to get a close look at one — and learn more about the ones that really are a hazard. The asteroid is called Apophis. It's a near-Earth asteroid that is a type called a chondrite, essentially a stony body that has high silicate content and few metals. It is about 330 meters across, and it's due to pass the Earth in 2029."

spectrography (AKA: Spectroscopy, Spectrometry, Spectroscopes) is definitely part of it. The orbit also gives them an idea of the mass of the asteroid which helps confirm that they the surface materials aren't too dissimilar to the inner makeup (because spectography can only detect the surface composition). Then they use examples of similar asteroids that have fallen to earth (I know "meteoroids") to refine the guesstimate on the makup a bit further. The only thing they can't make and educated guess on y

Because its orbital properties have been very well studied due to the potential if civilization altering impact. We know its approximate volume and mass. this gives us a fairly good clue about its composition because a mostly metal asteroid would be much more dense.

Not really, no. Not only we don't know its orbital properties to desired levels - simply knowing orbit won't really give you a very good mass of some point body, you need to observe a satellite of said body.

Volume / size and mass are usually estimated from brightness and spectroscopy (comparing the latter with samples we have on Earth)

We have a good idea of the composition of asteroids in general, from meteorites, planetary formation models, etc.

We believe Apophis is chondritic because based on its apparent brightness and the way that brightness varies, we have a decent estimate of its size and albedo. If it had a different albedo it would indicate a different composition.

Of course, as with all remote observations based on a lot of educated guesses, there is a chance its wrong. However, if it is its probably a pathological case we could never gotten right, and that would make it even more interesting to visit.

We have a good idea of the composition of asteroids in general, from meteorites, planetary formation models, etc.

We believe Apophis is chondritic because based on its apparent brightness and the way that brightness varies, we have a decent estimate of its size and albedo. If it had a different albedo it would indicate a different composition.

Of course, as with all remote observations based on a lot of educated guesses, there is a chance its wrong.

It is a little better than a wild ass guess. This particular asteroid happens to pass fairly close to the Earth from time to time and is also studied a bit more carefully due to its predicted potential to strike the Earth.

Yes, there is a chance it could be wrong, but there have been other asteroids which have been studied much more carefully and have even had physical probes go near or even land upon them for various kinds of scientific studies. Based upon those studies as well as meteor samples it seems

The speed, relative to Earth, during the encounter will be quite high - so a probe / lander / etc. allowing for really close study would need to get quite a kick from its rocket. And very rapidly (basically ruling out more efficient means of propulsion, those tend to have very low thrust) Probably much larger than sending it to some more optimal (regarding transfer orbits and delta-v) targets, a thing... which we are already doing!

If it turns to be practical, another nice target is good to have of course.

Send up 3 rockets tethered together by cables meeting at a common midpoint into the path of the asteroid. Boom, asteroid hits cable, probes get accelerated by asteroid to matching speed and are dragged off being the asteroid, providing observations for a long time... what could possibly go wrong?

I never really considered OTRAG to be African... certainly no more than Ariane 5 being South American (or Soyuz - Asian). Too bad it didn't even really get a chance..

And hopefully no more of

Nkoloso, at least from the evidence we have to go on, was something closer to a cargo cult leader than a scientist. What remains fascinating to us today is that he drew on the sublimity of space travel -- not religious sentiment -- to win friends and influence people. It's a reminder of the power that space travel had in the popular imagination of the 1960s.

The asteroid isn't simply one big rock - it seems to be a orbiting pile of rubble that has coalesced into a single object. The cables would probably just cut straight through - though they might snag on one of the larger rocks (50m radius) and apply some force onto it.

Have you ever watched video of a bola [wikipedia.org] being used to take down game? The weights at the ends of the cords whip around at increasing speed as they wind around the legs of the target. The average orbital velocity of Apophis is 30 kilometers a second, so that's the relative speed between the probes and Apophis when it hits the cables. If you ever played tetherball as a kid, you'll remember that the ball speeds up as it winds in to the pole, so the probes might well double the initial relative velocity by the ti

The speed, relative to Earth, during the encounter will be quite high - so a probe / lander / etc. allowing for really close study would need to get quite a kick from its rocket

It would probably be done in a roundabout way, first sending the probe in an interplanetary trajectory, to get gravitational assist [wikipedia.org] from another planet. Then it would do a close fly-by to the moon to get the required orbit inclination.

TFA states that the mission would have to be launched in 2021 to reach it by 2029.

Which in the end means that the goal of reaching it during flyby is quite... irrelevant. We might "just" treat it as another very interesting near-Earth object, to be closely studied not necessarily starting from 2029 (hey, it would be of course great if we could get the funding and the mission reaching it even sooner!) - one which does have higher priority due to its risks (and how a beacon on its surface could be useful), but again: nothing too special about the encounter.

(but you might start by building a ship with a hull not constrained by Archimedes' principle... its over 2 thousand years old, surely should be easier to ignore; those airplanes from "our" times [goo.gl], depicted in works of fiction from mere ~130 years ago, shouldn't be too far away now, too - because reality [wikimedia.org] is just too boring)

Although "The Relativity of Wrong" is one of my favorite Asimov essays, i wouldn't rule some changes in basic physics yet.

The situation now is very similar to that in the second half of the nineteenth century. Then there existed a strong consensus that Newtonian physics were the last theory, but two facts spelled problems against that view: the inability to reconcile Maxwell's equations with Newtonian physics and the Michelson-Morley experiment.

Do not forget to mention how, if anything, the realization of the consequences of Michelson-Morley experiment (and also the then triumphant wave theory hitting some dualities) had shown also many further limits of our world. And those effects were, ultimately, quite large.

If the Pioneer anomaly exists, it's exceedingly minuscule. Sensible proportions of dark matter and dark energy dictated by cosmological models... surprisingly in line with those suggested by observations. Or, one of my favorites: how i

I think the speed of light limitation is very fundamental, based on mathematics alone: IF space and time are quantized, the Courant condition [wikipedia.org] will not let waves propagate faster than a certain speed.

For interplanetary distances, a 20 Megawatt fission reactor powering a VASIMR engine is all you'd really need. As for interstellar distances, a slow nuclear-pulse orion-type ship would be the best investment. For some reason, I suspect *effective* FTL (e.g. not actually going the speed of light- side stepping it, such as a worm hole) is possible, but it is much further away then sub-light and near-light interstellars.

Most Orion design studies were about interplanetary travels. Orion is barely able to do "fun" interstellar - the most advanced designs limited to ~0.1c, in the range of a human lifetime to the nearest stars. But expect few of those lifetimes.

If we ever try direct approach - the colonists might be miniaturized and in deep hibernation [wikipedia.org] (we can already do that last dream!). IMHO most likely just spreading gradually, over thousands of years, further and further into the Oort cloud (estimated one trillion come

I know about the general 0.1c speed limit- honestly, I think it's fast enough to be practical when compared with the multi-millennial travel times of conventional rockets. If you did put the colonists in stasis, it's a decently fast way of headed to the stars. I've always thought that slow STL (that is, below 5% c or so) colonization plans were a waste of resources- even if you can mine from say an asteroid you're riding there. Nothing's wrong with slow interstellar colonization, ala firefly, but ideally we

I think it doesn't make much difference. What is "ideally" and why would it matter? Once some homo sapiens are in a different system than you, they are almost as well as nonexistent (recollect the relations of distant human populations before the Age of Discovery, before suitable vessels... which most likely won't ever become available for interstellar; similar thing, to a large degree, would happen even with outer planets of our system - not to mention scattered disk or Oort cloud), except for some (why wo

I get your arguments, and agree with most of it about resource waste for conventional manufacturing techniques. The embryonic ships also always seemed a good idea to me. But as far as the interstellar class orions, I think you're underestimating advances in the next hundred years or so. Picture it from a perspective into the fairly long term future, with a manufacturing system completely restructured by nanotechnology. Your ship fires a capsule of nanites into an asteroid or comet with the suitable resource

I think it would be much better to launch the probe prior to the approach of the rock, and let the rock catch up to it from behind. That or figure out a way to use the moon and Earth to slingshot a probe up to the necessary speed (I suppose if this we possible, we'd do it for every launch we currently make).

That's not "letting the rock catch up to it from behind", that's "letting the rock pass it, quite rapidly". And you cannot slingshot via body around which you are orbiting, that in itself requires already relatively fast passes / what we're doing with pretty much every interplanetary probe (also using Earth, but as, for one hypothetical example: 1) launch from Earth 2) slingshot during Venus flyby 3) second Venus slingshot 4) Earth slingshot 5) Jupiter slingshot 6)... )

I don't see the fundamental problem with launching a probe well beforehand, and then using a slower drive or various tricks in order to bring it up to the required speed over a period of time. However, I suppose then you're not really taking advantage of the asteroid coming so close to Earth either.

As I said, quite a kick (one of more powerful rockets used, fairly small probe) - plus it's much closer (possibly not enough, you would need to do calculations) than it looks; that escape velocity of New Horizons doesn't include how, with Apophis approach, effects which often are used to ease getting into orbit, might get in our way; or change of orbital inclination around the Sun. Plus exceptionally small launch window.

As a proof of concept of the manipulation of large nearby objects for commercial or planetary defense why not attempt to capture it into some not too remote orbit? I mean, "what could possibly go wrong?" Think of it as keeping a cue-ball handy for the next object that we want to redirect. Or stick telemetry on it; or a kick-ass telescope. Or mine it for unobtainium. If we don't learn to screw with the toys nearby we'll never move on to the proper human hegemony.

We could also move it into a low earth orbit and use it to sweep paths through all the obsolete satellites and other space junk that is up there. Maybe sell the naming and advertising rights to the highest bidder too.
I personally look forward to watching the Cialis Erectoid flying overhead.

Hard to do! It's speed is about 31 km/s...geosynchronous orbit is more like 3 km/s. So delta V is about 28km/s...for an asteroid with a mass of 2.7×10^10 kg, that's a kinetic energy of about 1E19 J or around 2.5 billion tons of TNT (2.5 gigatons).
Yeah...that's a lot.

Yeah, just another fantasy... it's no wonder people are disappointed, after all the works of fiction they're attacked with, by our great achievements in space.

Well, there might be one doable mechanism - transfer of momentum to capture one element of binary asteroid. Still far from trivial, especially if such object needs to be redirected (because there doesn't seem to be one readily available). And for doubtful gains.

It's orbital velocity may be near 31 km/s (relative to the sun), however it's velocity relative to earth (which would be the figure you're citing for geosynch orbital velocity) is not that great. Earth's orbital velocity is about 1 km/s lower than that. Of course, you can't say that the relative velocity between the two is the difference since this is quite obviously a 3 dimensional problem.

However, you can say that this is within the range of velocity of a geosynch satellite (30km/s +/- 3km/s) relative

Well, we do have something like 50,000 nuclear warheads we (hopefully) don't ever plan on using. At an average yield of about 400MegaTons each we should have enough as long as everything is planned and the blasts are as focused as possible. How about we land a shuttle on the asteroid, drill a shaft to act as focus for the blast energy, then set off several weapons from within the asteroid to redirect it's path. Maybe we can hire Bruce Willis do to the drilling!

One of the reasons we would not want to do this (change the path of the asteroid), as Carl Sagan talked about (I believe in the COSMOS TV series), is because if we could, it means we would also have the technology to direct the course of the asteroid into the Earth. I'm not sure if this is the only reason we have not yet tried such a thing (perhaps we've just never had such an opportunity), but I think some are hesitant to explore this potential doomsday weapon.

One of the reasons we would not want to do this (change the path of the asteroid), as Carl Sagan talked about (I believe in the COSMOS TV series), is because if we could, it means we would also have the technology to direct the course of the asteroid into the Earth. I'm not sure if this is the only reason we have not yet tried such a thing (perhaps we've just never had such an opportunity), but I think some are hesitant to explore this potential doomsday weapon.

Yes, if we don't do it, then we'll never figure out that we can do it... wait...

Those analyses are relatively easy to do, and you're not going to change its trajectory significantly unless you really mean to.

In order to do it with a ~500 kg spacecraft you have to hover about 200 meters away from the asteroid with your engines thrusting essentially continuously for around a year. If you're not close enough to have to worry about hovering, or if you're trying to do a landing, no reasonably sized spacecraft is going to make a difference.

In my mind, at a distance the mass of an object would include things that are in orbit around it - in terms of how it interacts with things far away gravitationally. Whether or not this adds up to anything significant over the course of the object's millions of miles of orbit - I'll give you that I could imagine that the difference is insignificant.

Well, as long as the mass of the object is negligible compared to the body its orbiting (in this case, the asteroid is absurdly smaller than the sun), then the mass of the body has no effect on its orbit. More specifically, the force is proportional to the mass so that the acceleration is constant regardless of mass.

The only time it will make a difference is for non-gravitational forces like solar radiation pressure or atmospheric drag. Then the surface area of the spacecraft will be much smaller than the

What's with the exotic asteroid names? Just once, I'd love to see them name an extraterrestrial body "Bob". I can see the headlines now: "Bob threatens impact with Earth". Much less scary than "Apophis threatens to wipe out all life on planet!".

What's with the exotic asteroid names? Just once, I'd love to see them name an extraterrestrial body "Bob". I can see the headlines now: "Bob threatens impact with Earth". Much less scary than "Apophis threatens to wipe out all life on planet!".

Hurricanes (and Storms) have that feature.Given that my name is one of the chosen Storm names (but it's not Bob), I am not sure if I would prefer to have a headline that said "Bob Kills 30,000, Leaves Millions Homeless" or "Bob is a Dud"

What's with the exotic asteroid names? Just once, I'd love to see them name an extraterrestrial body "Bob". I can see the headlines now: "Bob threatens impact with Earth". Much less scary than "Apophis threatens to wipe out all life on planet!".

I like this idea. It opens up so many possibilities for impact remediation mission names. For example, Cometary and asteroidal Orbital adjustment Under Controlled Hazards (COUCH). I'm already picturing the headline: Scientists prepare COUCH for Bob to crash on.

By way of Wikipedia, this article on Astronomy.com [astronomy.com] seems to point out that indeed the connection to SG-1 is there in terms of how this asteroid was named.

It is sort of ironic too as there was an episode of SG-1 that dealt with an asteroid that was purposely deflected to hit the Earth by that Goa'uld system lord of the same name. That the mythology of the Egyptian god fits so well and the name up to that point had not been previously used on an asteroid only made it a perfect fit. It certainly isn't a name

Since when is 20 years from now "soon"?
On the other hand, if there are space pirates out there Apophis is just right to use for blackmail. "Nice planet ya got there, be too bad if anything happened to it!". Although there is the question of what we have that they they would want.

Now subtract time to get the public's attention, time to direct that attention towards political action to fund a mission, time to arrange the prime contracts for the mission, time to design the system well enough to let subcontracts, time to develop the components, time to integrate the components, and time to launch the vehicle and travel to the asteroid.

I remember in late 1970s of looking through a NASA STAR reports abstracts, there were a series of reports on asteroid retrieval. I think it discussed these in terms of mining for various metals and I think of of these suggested placing an asteroid in earth orbit. One of these days I'll find that book (along with other archival stuff like my CB radio license). I did a quick search but didn't find these (yes I know I gotta make it specific but then if I can do that then I already have the reports!). I did see

Apophis is a great opportunity to put an asteroid in orbit. The technology would allow us to put high-value mining resources in easy reach of orbital platforms. The result would be vast mineral resources available for engineering works, without costly launch fuel requirements.

I love that show (Stargate). Not as good as Babylon 5 or Deep Space Nine, but still a great series. Always kept me on the edge of my seat, and I enjoyed the "exploring new worlds" aspect that other shows have abandoned.

- Like the planet with the strange white men that talked to flowers- Or the time they accidentally opened onto a black hole gate (Never understood why they were not able to rescue the other SG team.)- Or the first time they met the replicators

Or the time they accidentally opened onto a black hole gate (Never understood why they were not able to rescue the other SG team.)

Apparently you didn't like the show enough to understand why they couldn't rescue the other team. It had to do with the gravity well of the black hole causing time dilation. What they were seeing had already taken place.

In fact, the event horizon got into the SG center and was in the process of doing its thing until a small nuclear device was dropped into the Stargate